Air heater



Jime 19, 1928.- 1,673,992

* w. H. OWEN AIR HEATER Filed'Aug. 25, 1924 2 Sheets-Sheet l June 19,1928.

w. OWEN AIR HEATER 2 Sheets-Sheet 2 Filed Aug; 23, 1924 l W 21AM 4w 1 o1T 1 X X w 0 v a 4 W m 1 w M w 4 m m 4 x 7Q \iTL a m ai mm ufvi 1% 3 LIEPatented June 19, 1928.

WILLIAM HENRY OWEN, OE WIMIBLEDON, ENGLAND.

AIR HEATER.

Application filed August 23, 1924, Serial No. 733,833, and in GreatBritain September 3, 1988.

This invention has reference. to air-heaters and relates moreparticularly to apparatus for pre-heating air for combustionbyextracting heat from waste gases.

The mvention may be applied to furnaces of all kinds, and also forheating air to be used for any purpose whatever, such asthe drying ofpaper, grain or timber.

The invention has for its main objects to improve air heaters in whichthe heating elements consist of sheet metal plates, as distinguishedfrom tubes, and also to ensure cheapness of construction and highefficiency of heat transmission, as well as facility for cleaning,inspecting and renewing the heating elements.

a A feature of the invent-ion is thatthe plates are very thin, as thinas one fiftieth of an inch or less and may be made of noncorrodiblemetal such as alloys of iron, chrome ornickel or of nickel alone or ofaluminium according to the natureof the waste ases to be dealt with bythe heater.

Anot ier feature of the invention is that preferably the plates arearranged closely together, for example the spaces between them may be asnarrow as an eighth of an inch across but this distance may depend uponthe length of the plates, especially the. length in the direction of theflow of the gases, or vice versa the length of the plates may bedetermined by the width of passages, provided that the length of theplates is not less than from to 100 times the width of the spacesbetween them.

This relative length maybe obtained, in some cases by arranging theheating ele ments in two or more tiersor stages in series in thedirection of the gas flow, the gases preferably passing through thesections.

According to the invention the heating elements consist of thin metallicsheets or plates which may be assembled in permanent groups or bundlesto form elements or sections, consisting of two or any convenient numberofsheets, which are fixed or contained in an envelope or casing in sucha way as to give ready access for cleaning, in-

specting and renewing.

The sheets or plates are separated from each other by peripheralpackingpieces or strips of metal or any other suitablematerial such asasbestos, leaving alternate passages for air and gases. The said packingpieces are cut away or omitted where neces- Alternatively, the elementsmay take the form of separate cells which may be separated from eachother by suitable distance pieces and may be assembled in bundles,groups or sections consisting of any convenlent number of cells.

The groups of cells or plates may be held together either by throughrivets with wash ers or distance-pieces where required, or by severalcross-strips of metal or light angles welded on to the plates or in anyother conven ent manner. Or the plates may be made up in a continuous orsinuous fashion, opposite'edges of a plate being connected to itsneighbours to the right and left respectively, by welding or otherwise,leaving alternate spaces for the air and gases, the remaining edgesbeing closed where necessary by packing pieces or other convenientmeans.

Strips welded on to the plates or other convenient means would be usedfor giving" rigidity to the groups or bundles. In all cases suitablepacking strips would be used to prevent leakage of air or gases to thecasing or to each other.

The waste gases and the air may be caused to traverse their respectivepassages in different directions for instance oppositely to give acounter-current effect. Guide strips may be fixed in the air passages tocause the air to pass through without eddies or loss of pressure and togive stiflness to the plates. The sides of the plates or cells mayhowever be suitably indented inwards or provided with ribs or ridges toform guides and to stifl'enthe plates.

In order that the invention may be clearly understood and readilycarried. into effect reference will now be had by way of example to theaccompanying diagrammatic drawings, in which Figs. 1 and 2 arerespectively a side-view and transverse section ofabundle, group orsection ofthe air heating elements.

Figs. 3 to 8 represent modifications hereinafter referred to.

Figs. 9 and 10 are sections at right angles 105 heater such asreferred-to a marine boiler.

Referring more particularly to Figs. 1 and 2 these show the method ofbuilding up the bundles or sections of the elements, which are intendedto be assembled in the casing of the apparatus. The plates are shown at1, the packin strips at 2 and the rivets at 3, whilst binding strips orangles are shown at 4. The comparative width of the spaces between theplates is shown considerabl exaggerated for the sake of clearness. eopenin left for the entrance and exit of the air are shown at 5 and 6respectively. The gases pass in the direction of the arrows marked 7.

- In Fig. 3 the guide strips, ribs or stiffeners 8 are shown between thesheets. They serve to guide and distribute the air and to spread itevenly between the plates and also act as distance pieces between thelatter to ive them stiffness and support. The may be welded or otherwisesecured in t e air passages.

A method of making these uides and stitieners 8 by groovin or in entingthe plates is illustrated in ig. 4. The indentations may be in one or inboth plates.

Figs. 5, 6 and 7 illustrate diflerent constructions of the individualcells. The edges are shown welded to each other at 9 and turned orheaded over at 10. The cells may be made up into bundles by usingbinding stri s or angles as at 4.

1g. 8 shows a long sheet 1 folded to ive a continuous or sinuousconstruction. fiinding strips (as shown at 4) or packing ieces may beused to hold the sections rigidly together. The spaces between theplates at the edges may be closed when required by strips 11 welded in.

Fig. 9 is a sectional view of the caszng for containing the grou s ofelements. 1

and 2 are respectively t e outlet and inlet air ducts. The heatingelements are carried by the angle-irons 4 and are inserted andwithdrawn, cleaned and inspected throu h the doors 4", which may besecured by stu 5, bolts or by hinges and catches or in any otherconvenient way.

In some cases where the air for combustion is heated in two stages, andused in portions one hotter than the other, the hotter ortion wouldtraverse the whole of the eatin surface and would leave the heater at te gas-inlet end, the cooler portion being taken away to the furnace orfurnaces at an earlier point, exit ducts being provided to suit thelocation of the heater.

Thus in the example under consideration, the cooler portion may be ledaway by a duct 13 as shown by dotted lines. Steam pipes for blowing outthe soot are shown at 14.

The integral by-pass is indicated at 5", Fig.

10. There may be as many of these passa es as necessary. The walls 6 arecarried hc full depth between the top and bottom angles 4 and help tostiflen the structure. The passages communicate with the gas inlet at 8and the gas outlet at 9*, and are each fitted with a damper 10*,operated by a handle 11*.

A door 12 may be provided between the air ducts or passages.

Fig. 11 shows a modification in which the heating elements are arrangedin tiers or stages, marked 1 and 2' respectively. The air enters the topstage at 3, passes to the bottom section by way of the passage 4, andleaves by the duct 5. The duct 6 shown in dotted lines is the exit forthe cooler air as in Fig. 9. The arrows 7 show the course of the air andthe arrows 8" the course of the gases. Doors 4* are provided forcleaning etc. It will be seen that the air-ducts on the sides of theheater conduct the air from an upper tier or section to the one nextbelow, and cleaning and inspection doors may be provided for each tier,or common to all the tiers as convenient. The heating elements may bemade of different materials when required to resist the difierentcorrosive effects, in different arts of the gas passages, of certainkinds of waste gases.

In fact different metals may be used for the plates in different groupsor in different sections, to better resist corrosion, especially, wherethere is liability to a deposit of moisture or liquid at the outlet end.

Fig. 12 shows the arrangement when the course of the air is at rightangles to that of the gases. The arrows 1 show the direction of the airand the arrows 2 that of the gases. A door 4* gives access to theelements. In some cases these latter may be placed in the gas passageleading to the heater.

When the heater is used in conjunction with-steam boilers of thecylindrical marine type, it may (as shown in Fig. 13) be convenientlyplaced as at I) immediately above the smoke-box or boxes e so that thewaste gases pass up through it as shown by the dotted arrows, direct tothe chimney. The inlet and outlet air-ducts marked 0 and d respectively,may be then arranged between the heater and the end of the boiler a,with suitable connections to the ducts leading to the furnaces, so thatthe air flows practically directly counter to the waste ases as shown bythe full-line arrows. The inspection and cleaning doors in this case maybe conveniently arranged at the front as shown at f so as to be easilyaccessible, whilst steam ipes g for blowing out soot may be provic edwhere desirable.

no or more by-passes may be arran ed for each smoke-box, to be used whenlig ting up or when otherwise required.

if rials Ertherhflturafi -induced or forced draught, coihbinatift'ini'of forced and induced dr ught may b u'sed. it 'will seem that in casesWhere the is used in two portions efother, the hotter portion lieater ator near the gasinlet end, the other portion being taken away at anearlier point, suitable exit ducts being provided, as mentioned inconnection with 5 and 6 Fig. 11 of example. Also the cells may consistof two plates each, or of one plate doubled over, distance pieces beingused between the edges of the latter being bent or beaded over eachother, or being welded together, thus giving a cheap air or gas .tightconstruction.

The casing containing the heating elements may consist of a box ofrectangular cross-section, and be open on two opposite sides,communicating respectively with the 1 gas connections to the boiler orfurnace and.

the chimney. It is of course provided with the necessary inlet andoutlet ducts for the air communicating with the air passages between theelements. It is provided with doors to give access for cleaning the gaspassages and for inspecting 'or renewing the heating elements. Thesedoors are preferably placed on the side of the heater opposite to thaton which the air ducts are arranged.

As indicated the air may traverse the air passages in a direction atright angles or transversely to that of the gases. The doors for accessand cleaning may be placed in the gas ducts either before or after theheater, and the elements may be withdrawn into either of these spaces asconvenient. In all cases the elements would preferably be connectedtogether in such a way as to leave thegas passages exposed when theinspecting door is opened, thus allowing the operation of cleaning bhand to be performed in sections during t e working of the boiler,suitable packing or other means being provided when necessary to preventleakage.

Any suitable steam or compressed-air arrangement for blowing the sootout of the gas passages may be used. The steam jets may be mounted onpipes movable longitudinally or in a circular direction, in order tosweep over the entrance to the gas passages.

The passages such as 5 Fig. 10 acting as by-passes and provided withvalves or dampers between the groups of plates are to allow the gases topass directly to the chimney when required, for instance when work,- ingwith natural draught and when lighting up a cold boiler or furnace andwhen the mechanical draught would not be available.

A separate by-pass may be provided for each furnace or grate whendesirable as in the case of a cylindrical marine boiler, and suchby-pass forms an integral part of the heater.

When used in conjunction with a cylindrical marine boiler, the heatermay be placed immediately above the smoke-box with the plates parallelwith the axis of the boiler and with both the inlet and outlet air ductsarranged between the heater and the boiler shell, with the cleaning andinspecting doors on the front of the heater giving convenient accessfrom and allowing the plates to be withdrawn into the stoke-hole.

In such a case the inlet and outlet air ducts may be respectively onsides of the heater opposite to each. other, or the plates may run in atransverse direction, that is to say at right angles to the axis of theboiler, the air entering the spaces between the plates froin a chamberon or near to the boiler centre line.

The gases flow vertically upwards from the smoke-box, suitableconnectionsfor leading the heated air to the furnace being provided.

When the plates run transversely across the boiler the by-passes would"also be transverse to the boiler and may be fixed near the front ornear the back ofthe heater, isolating walls running-up to the top of theheater, and dampers being provided for each smokebox. Y

The heater apparatus may be applied to one furnace only, or to anynumber of furnaces working to ether and having a common waste as ueleading to a common chimney, an forced or induced draught or acombination of these may beused.

Obviously the above arrangements may be modified in various ways incarrying the invention into practice without departing from the generalnature thereof.

I claim:

1. In an air-heating apparatus the combination of an outer casing,removable elements inside same comprising very thin parallel metalsheets, air inlets and outlets for the alternate spaces, hot-gas inletsand outlets for the intervening spaces, passages arranged between theremovable elements to form by-passes for the hot-gases, and means forcontrolling the flow of such gases through said by-passes.

2. The combination in a heat-exchanging apparatus of an outer casing,independent removable air-heating elements in said casing, said elementsbeing formed of thin metal sheets with narrow spaces forming alternatehorizontal and vertical passages between them, the horizontal passagesserving for the air to be heated, whilst the intervening verticalpassages serve for the hot waste gases, inlets and outlets at the sameside of the apparatus for the air to be heated, and doors on theopposite side thereof for the insertion and withdrawal of theair-heating cells both at the rear of said elements, and elements,substantially as described. steam-blowers in the spaces between thetiers l0 The combination in a heat-exchanging for injectin steam jetsinto the intervening appm'atus, of an outer casing, removable spaces, sotliat each tier has its own set of 5 elements arranged as tiers oneabove the blowers for the purpose of keeping the same other, saidelements comprising cells of flat clear, substantially as described.metal sheets with narrow spaces intervening In testimony whereof I atlixmy signature. between them, air-inlets and out-lets for said WILLIAMHENRY OWEN.

